Envoy: dns_filter_integration_test flake

[mattklein123]

FAIL: //test/extensions/filters/udp/dns_filter:dns_filter_integration_test (see /build/tmp/_bazel_envoybuild/b570b5ccd0454dc9af9f65ab1833764d/execroot/envoy/bazel-out/k8-dbg/testlogs/test/extensions/filters/udp/dns_filter/dns_filter_integration_test/test.log)
INFO: From Testing //test/extensions/filters/udp/dns_filter:dns_filter_integration_test:
==================== Test output for //test/extensions/filters/udp/dns_filter:dns_filter_integration_test:
WARNING: Perftools heap leak checker is active -- Performance may suffer
[==========] Running 10 tests from 1 test suite.
[----------] Global test environment set-up.
[----------] 10 tests from IpVersions/DnsFilterIntegrationTest
[ RUN      ] IpVersions/DnsFilterIntegrationTest.ExternalLookupTest/IPv4
[2020-07-29 14:57:16.442][25][error][main] [source/server/worker_impl.cc:49] failed to add listener on worker: cannot bind '127.0.0.1:34664': Address already in use
[2020-07-29 14:57:16.442][23][error][config] [source/server/listener_manager_impl.cc:685] listener 'listener_1' failed to listen on address '127.0.0.1:34664' on worker
[2020-07-29 14:57:26.424][16][critical][assert] [test/integration/integration.cc:500] assert failure: 0. Details: Timed out waiting for listeners.
================================================================================

[mattklein123]

Haven't looked yet but there may be some issue with how we are initializing UDP tests as I'm pretty sure this is using port 0.

[abaptiste]

I think this could be due to a missing reuse_port option in the test config. I've added this in https://github.com/envoyproxy/envoy/pull/12085. I'll keep an eye out to see whether I this is still reproducible.

[mattklein123]

Yeah I think reuse_port would likely fix it. The issue is fundamentally that https://github.com/envoyproxy/envoy/blob/544a414ff26a6bda516a48651d64b50226b43cb5/test/extensions/filters/udp/dns_filter/dns_filter_integration_test.cc#L63 is flaky.

[abaptiste]

/assign abaptiste